1. Field of the Invention
The present invention relates to a power supply circuit and a semiconductor device having the same.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electro-optic device, a semiconductor circuit, and an electronic appliance are all semiconductor devices.
2. Description of the Related Art
A power supply circuit such as a switching regulator has been conventionally used for a wide range of electronic appliances typified by an image pickup device and a display device. A portable information terminal such as a mobile phone or a game machine incorporates a power supply circuit. A reduction in size for a reduction in weight of such a portable information terminal has been desired, and moreover a reduction in power consumption thereof has also been desired in order to achieve a long-time operation in which a battery is used as a power supply.
A digital control circuit used for a power supply circuit can have fewer components than an analog control circuit, whereby the size reduction is possible.
However, there is a problem in that the power consumption of the digital control circuit is larger than that of the analog control circuit.
Patent Document 1 has described a reduction in power consumption due to an intermittent operation of a power supply circuit portion when the load is small, for example when a device is in a sleep mode.